1. Field of the Invention
This invention relates generally to sampling systems for downhole use, such as for sampling well fluids in the oil and gas industry, and in particular to carriers for pressure compensated single phase samplers for use in drill stem testing application.
2. Background Art
Fluids may issue from geologic formations into a well at high pressures and temperatures. To raise these fluids to the well surface for sampling without the fluids undergoing phase change, pressure compensated single phase samplers are used. Such samplers typically include a piston-cylinder sampling chamber and a gas reservoir that supplies high pressure gas to maintain the pressure in the sampling chamber at the sample collection pressure. A rupture disk is used to trigger the operation of the sampler. One example of a single phase sampler is described in the United Kingdom Patent GB 2 252 296, filed on Dec. 5, 1991 by inventors Massie et al. and entitled “Fluid sampling systems,” which is incorporated herein by reference. Other samplers are disclosed in U.S. Pat. Nos. 5,609,205 and 5,337,822 issued to Massie et al. and entitled “Well Fluid Sampling Tool,” and U.S. Pat. No. 5,901,788 issued to Brown et al. and entitled “Well Fluid Sampling Tool and Well fluid Sampling Method,” which are all incorporated herein by reference. Such samplers preferably have a small diameter so that they may be used in wireline operations.
Tubular carriers that are arranged for running multiple single phase samplers into a well are known in the art. Such carriers are used, for example, in conjunction with a drill stem test. Typically, a number of slim single phase samplers are circumpositioned about the circumference of the carrier, leaving a clear through-bore for wireline operations. Two or more samplers may be actuated by annulus pressure using a common rupture disk, if desired. By outfitting one or more of the individual single phase carriers with annulus rupture disk actuators having differing burst pressures, multiple well samples may be taken at different flow periods. Examples of such drill stem test carriers for single phase samplers include Schlumberger's Oilphase DBR SCAR Sample Carrier, Expro's Petrotech SmartCarrier, and Halliburton's Simba and Armada carriers.
It is desirable to use existing single phase samplers in a carrier having an arrangement wherein the maximum outer diameter does not exceed five inches so that the drill stem test carrier may be run into seven inch heavy-walled (38 lb/ft, 0.540 inch wall thickness, 5.920 inch inner diameter) well casing. Although the Schlumberger's Oilphase DBR SCAR Sample Carrier is available in both 5.25 inch and 5.5 inch outer diameter models, each carrying up to eight samplers for a combined sample size of 2400 cc, the samplers are partially enclosed by a cylindrical housing, which subjects the samplers to potential mud entrapment around the sampler inlet ports. Mud entrapment can result in the first portion of the sampled volume being compromised with mud/completion fluids. Expro's Petrotech SmartCarrier is available in a 5.0 inch model that includes four samplers for a combined sample size of 2160 cc. The SmartCarrier sacrifices sample volume to achieve its small diameter. Moreover, the SmartCarrier has a full bore inner diameter of 2.0 inches rather than the 2.25 inch, which is less than desirable for wireline operations. Halliburton's Simba carrier is designed for use within seven inch casing and has a 2.25 inch through bore, but it is limited to two samplers for a combined sample volume of 1200 cc. Finally, Halliburton's Armada sampling system includes a carrier having a 5.375 inch outer diameter, 2.25 inch through bore, and can run up to nine one-inch samplers for a combined sample volume of 3600 cc. The Armada achieves this capability by using a common nitrogen section for servicing all of the samplers. For this reason, the Armada is characterized by considerable potential leak paths and is complicated to manufacture, assemble and test.
3. Identification of Objects of the Invention
A primary object of the invention is to provide a carrier for single phase samplers having a maximum outer diameter of 5.0 inches, a through bore of 2.25 inches, an overall length of approximately 39 feet, and a total sample volume of 2400 cc.
Another object of the invention is to provide a carrier for single phase samplers that may carry up to four single phase samplers.
Another object of the invention is to provide a carrier for single phase samplers that allows for simplified manufacturing assembly and testing.
Another object of the invention is to provide a carrier for single phase samplers that removes the need to machine the casing body of the carrier.
Another object of the invention is to provide a carrier for single phase samplers that reduces potential leak paths by minimizing the need for and number of internal seals within the carrier body.
Another object of the invention is to provide a carrier for single phase samplers that incorporates rupture disks in top and bottom subs.